1. Field of the Invention
The present invention relates to a medical device including a tubular instrument having a plurality of active joints for changing a position and an orientation of a distal end portion at an insertion portion.
2. Description of the Related Art
Recently, in treatment instruments that are inserted through a treatment instrument channel provided in an endoscope, medical manipulators having a plurality of active joints at a distal end portion or the like of a treatment instrument insertion portion have been proposed for the purpose of improving operability of operators. In the medical manipulators, the distal end portion of the insertion portion is moved in an operator desired direction by pulling or loosening a drive wire by a drive actuator and rotating the active joints, for example.
An operating range of the active joints of the medical manipulator can be limited by controlling driving of the drive actuator. Therefore, when the medical manipulator is used in an operation, a given region around a diseased part is set to a reference position. By performing control to limit an operating range of a treatment unit provided in the medical manipulator, safety with respect to the diseased part can be improved.
For example, Japanese Patent Application Laid-Open Publication No. 09-168519 discloses a system and a method for mapping a catheter electrode position within a patient's body. According to the patent document, a voltage is detected between a catheter tip electrode and a reference electrode to obtain a three-dimensional location of a catheter tip within the body.
Japanese Patent Application Laid-Open Publication No. 2002-65626 discloses a novel catheter, a system and a method for detecting contact of an electrode with tissue. The system of the patent document includes a multi-electrode catheter having a location sensor and a plurality of contact electrodes, and tissue contact is detected by comparing signals between a tip electrode to a return electrode versus signal between a reference electrode to a return electrode.
Japanese Patent Application Laid-Open Publication No. 2007-61612 relates to detection of skin impedance for detecting a position of an object placed within a living body, and discloses an apparatus for detecting a position of a probe having at least one probe electrode which is adapted to be inserted into a living body. According to the patent document, electric currents are driven between a plurality of electrodes on the probe and a plurality of electrodes placed on a body surface to obtain three-dimensional position coordinates of the probe based on impedance measurements.